The U.S. Justice Department said Tuesday it wouldn't pursue criminal civil rights charges against a white Milwaukee police officer who shot a mentally ill black man 14 times in a city park last year.

The department said in a news release that there was insufficient evidence to warrant charging Christopher Manney in the April 2014 killing of Dontre Hamilton, who was schizophrenic but not violent, according to his family.

According to Manney, who has since been fired, he encountered Hamilton in the park while responding to a call about a man sleeping there. Manney's attorney, Jonathan Cermele, has said the officer suspected Hamilton was armed and may have been more of a threat than he appeared when he stood up and raised his arms to be frisked.

Manney has said he patted down Hamilton and a struggle ensued. He has said Hamilton took away his police baton and attacked, prompting him to open fire in self-defense.

Police Chief Edward Flynn said at the time that the pat-down wasn't necessary, and he fired Manney for failing to follow department rules. A panel of police commissioners agreed with Flynn's decision.

The Justice Department said it based its decision not to charge Manney on eyewitness accounts, physical evidence, Manney's testimony and input from use-of-force experts. Federal prosecutors said they determined they couldn't prove beyond a reasonable doubt that Manney willfully broke the law.

Officials from the U.S. Attorney's Office of the Eastern District of Wisconsin, the Justice Department's Civil Rights Division and the FBI met with the Hamilton family Tuesday to let them know about the decision.

"We all know what to expect when it comes to this city," Hamilton said, speaking for the family. "We know injustice; we've seen what injustice looks like before Dontre."

In a rambling, emotional message, Hamilton at times called for political action and unity and at times warned that unrest could take the streets if changes weren't enacted. "I'm calling out everybody in my community," he said and asked people to attend an afternoon rally and march planned ahead of a nearby Republican presidential debate.

Flynn, meanwhile, said his department has been committed to reform and has reduced uses of force, citizen complaints and the number of people injured by police.

The Rev. Jesse Jackson called Friday for federal investigators to launch a broad review of the Milwaukee Police Department's policies after a white officer shot a mentally ill black man to death this past spring.

Jackson appeared on the steps of Milwaukee's federal courthouse late Friday afternoon...

He said he has requested a Justice Department partnership and examination "to demonstrate that I am absolutely convinced that external review of our operations, our policies, our procedures and our practices will verify the progress we make and the fact that we are an agency committed to reform."

Federal officials began to review the case after the Milwaukee County district attorney decided not to file state charges against Manney.

Safran said Dontre Hamilton's family plans to file a civil rights lawsuit in federal court in the near future.

Hamilton's mother, Maria Hamilton, started a support group for mothers whose children have died in police encounters and took part in a "Million Moms" march in Washington last May.